The present disclosure provides a dimer formed by two polypeptide chains, with each of the two polypeptide chains comprising an antibody Fc subunit, wherein the dimer comprises two or more immunoglobulin single variable domains (ISVDs), at least one of the ISVDs is specific for PD-L1, and at least one of the ISVDs is specific for CTLA4.本發明提供一種由兩條多肽鏈形成的二聚體,所述兩條多肽鏈中的每條均包括抗體Fc亞基,其中所述二聚體包括兩個以上免疫球蛋白單可變結構域(ISVD),至少一個ISVD為PD-L1特異性的,並且至少一個ISVD為CTLA4特異性的。